ThinkUp stores this timezone in the config.inc.php file in this line:
$THINKUP_CFG['timezone'] = 'America/Los_Angeles';
As of beta 14, on every connection to the database, ThinkUp explicitly sets the database timezone to that value. Any date/times information for a given table should be stored in UTC as a MySQL DATETIME field. ThinkUp adjusts for the user’s timezone by using the #gmt_offset# token in SQL queries on select statements.